Motorola DSP56012 - Manual (Page 73)

Memory, Operating Modes, and Interrupts
Operating Modes
MOTOROLA DSP56012 User’s Manual 3-13
T states). When the DSP is driven by a stable external clock source, setting the SD bit
before executing the STOP instruction will allow a faster start up of the DSP.
3.5 OPERATING MODES
The DSP56012 operating modes are defined as described below and summarized in
Table 3-3 . The operating modes are latched from pins MODA, MODB, and MODC
during reset and can be changed by writing to the OMR.
The operating modes are described in the following paragraphs.
Mode 0 In this mode, the internal Program RAM is enabled and the bootstrap
ROM is disabled. All bootstrap programs end by selecting this
operating mode. This mode is identical to DSP56002 Mode 0.
Note: It is not possible to reach operating Mode 0 during hardware reset. Any
attempt to start up in Mode 0 defaults to Mode 1.
Mode 1 In this mode, the bootstrap ROM is enabled and the bootstrap
program is executed after hardware reset. The internal Program RAM
is loaded with up to 256 words from the parallel Host Interface.
Mode 2 Reserved.
Mode 3 Reserved.
Note: It is not possible to reach operating Mode 3 during hardware reset. Any
attempt to start up in Mode 3 defaults to Mode 1.
Mode 4 In this mode, the bootstrap ROM is enabled and the bootstrap
program is executed after hardware reset. The bootstrap program
Table 3-3 Operating Modes
Mode
MMM
C B A
Operating Mode
0 000 Normal operation, bootstrap disabled
1 001 Bootstrap from parallel Host Interface
2 010 Reserved
3 011 Reserved
4 100 Wake up in Program ROM address $0A00
5 101 Bootstrap from SHI (SPI mode)
6 110 Reserved
7 111 Bootstrap from SHI (I
2
C mode)